Centrifugal separator with hermetically closed outlet



United States Patent Ofifice CENTRIFUGAL SEPARATOR WITH HERMETI- CALLY CLOSED OUTLET Henric Wilhelm Thylefors, Stockholm, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden, a corporation of Sweden Application November 3, 1955, Serial No. 544,772 Claims priority, application Sweden November 10, 1954 2 Claims. (Cl. 233-1) This invention relates to centrifugal separators of the type having an hermetically sealed path through which the centrifugal rotor discharges into a stationary pipe. It has particular reference to an improved sealing arrangement for centrifuges of this type.

Centrifugal separators having hermetically closed inlets and outlets are used when it is desired that the liquid under separation be fed to and discharged from the centrifugal rotor without coming into contact with the outer atmosphere. This avoids contamination of the liquid with air and prevents mixing of the liquid with air and the resulting formation of foam, as would otherwise occur, for example, in centrifuging beer and milk. In such separators, it is a problem to lead off the separated liquid, against a variable counter-pressure, from a rotary element (the centrifugal rotor) to a stationary element (the discharge pipe of the centrifuge), as is the case, for instance, when separated beer is to be led from the rotor to a filter. When the filter is clean, the beer may be fed at a pressure of only 3 kg./cm. but subsequently when the filter has become clogged to a certain extent, the beer must be fed at a much greater pressure, for instance, kg./cm.

The joint between the rotary and the stationary elements. must be sealed against admission of air to the discharging liquid. For this purpose, the discharge end of the centrifugal rotor has in some cases been provided with a wearing ring which rotates against a stationary ring of carbon or other suitable material on the discharge pipe, the last-mentioned ring being spring-pressed against the wearing ring and thereby sealing the flow of liquid discharging through the rings. In another design, the discharge end of the centrifugal rotor has been shaped as a pipe fitting which extends concentrically with the discharge pipe into the opening of this pipe, the clearance between the pipe fitting and the edges of this opening being closed by a sealing ring, which may be a packing collar having a U-shaped cross-section. In these two designs, when it is desired to maintain a certain pressure in the discharge pipe of the centrifuge, it is necessary to feed the liquid into the centrifuge under a correspondingly increased pressure to compensate for the pressure drop incident to passage of the liquid through the centrifuge. Thus, the sealing means for the joint between the rotary and stationary elements is under a pressure which depends upon the counter-pressure in the discharge pipe; and this, of course, causes leakage troubles.

In still another prior design, the discharge end of the centrifugal rotor is provided with a pipe fitting which extends into the stationary discharge pipe, there being a sealing means between the rotary and stationary elements, as in the second design described above. In this third design, the end of the rotary pipe fitting is provided with a pump wheel operating in a chamber arranged in the stationary discharge pipe. The pump wheel is consequently rotated with the centrifugal rotor and increases to a certain extent the pressure of the liquid a coming from the centrifugal rotor, so that this liquid continues under increased pressure through the stationary discharge pipe. In this way, it is possible to reduce the pressure in the feed pipe of the centrifuge and still attain the same pressure in the discharge pipe. This results in an unloading of pressure at the outlet or sealing means of the centrifuge; and by providing vanes of suitable form and dimensions on the pump wheel, it is possible to attain such a pressure reduction in the liquid near the outlet packing that the inside of the packing is under approximately the same pressure as the outside, where there is atmospheric pressure. However, if the counter-pressurein the stationary discharge pipe rises considerably, as may be the case. with the above-mentioned beer filtration, the pressure in the feed pipe of the centrifuge must be increased to a corresponding degree, so that the packing under these circumstances will nevertheless be under considerable pressure. Therefore, the desired unloading of pressure at the outlet packing is not obtained.

The. importance of an unloading of pressure at the outlet packing or sealing means is apparent from the fact that the greater the pressure difference betweenthe two sides of the packing, the greater must be the pressure of the packing against the surface along which it slides, if no leakage is to occur. Such an increased pressure leads to a more rapid Wear of the packing and, therefore, to reducing its life. If the pressure difference between the two sides of the packing can be reduced to about zero, it will theoretically be almost impossible to wear out the packing.

The present invention has for its principal object the provision of a centrifugal separator having an hermetically closed outlet in which such an unloading of pressure at the outlet packing is obtained, and which at the same time enables discharge of the separated liquid against a varying counter-pressure without the pressure being changed in the feed pipe of the separator.

A centrifugal separator made according to the invention comprises a paring chamber arranged in the rotor and into which a stationary paring device extends, the discharge pipe of this paring device being arranged concentrically with the rotor axis. A collar packing having a U-shaped cross-section is fitted securely to the rotor body so that the packing rotates with its inner sealing surface against the outside of the stationary discharge If there is no pressure difference between the atmospheres on the two sides of the packing, the pressure of the packing may be about zero. It will thenbe practically impossible to wear out the packing.

In contrast to the present arrangement, collar packings used heretofore in hermetically closed separators have been secured to a stationary part and pressed against the rotating surface, usually by an initial tension in the collar as well as by the considerable liquid pressure acting upon it, with accompanying rapid wear of the packing.

If gas-emitting liquids, such as beer, are to be treated by means of the new separator, there can be a certain super-atmospheric pressure in the paring chamber, for instance 0.8 kg./cm. This, however, is only a fraction of the pressure which normally exists in the stationary discharge pipe of the centrifuge and which, in prior separators, acts directly upon the packing. However, if such Patented Oct. 28, 1958 a super-atmospheric pressure is present in the new separator;'the collar packing should be arranged so'that'its annular recess faces the interior of the rotor.

The life. of the collar packing can be further increased by arranging'for coolingandlubrication of the packing. Thiscan .be done, according to afurther feature of the invention, by providing the stationary paring device with a cylindrical projection whichiis concentric with the rotor axis and the'free edge of Which extends into the annular recess ofthe collar packing, and by providing a channel for supply of cooling liquid which opens into the annular space. between the. outside of the discharge pipe and the inside of 'the'cylindrical projection. In this case, the coolingliquid'supply can be obtained byarranging one or more apertures inthe wall of the discharge channel .of the paring device so'th'at'the liquid under pressure in the discharge channel can spurt into the above-mentioned annular space.- This' liquid sweeps along theiinsidebf the collar packing,fiows over the free edge of the abovementioned cylindrical projectiomand then joins the liquid present in the paring chamber.

For a better understanding of 'theiinvention, reference may-be had to the accompanying drawing, in.which.the single illustration isv avertical sectional view of the upper part ofa centrifugal separator embodying tat/preferred form of the present invention.

' In,the drawing, the reference numeral 1 designates the upperpartfof the rotor body or centrifugal bowl of the separator, whichpontains a paring chamber}. The paring chamber) receives arelatively light component of the feed material which is separated in the mainseparating chambertnotshown) of the rotor, the light. component flowing upward from 'this main separating chamber through' passage 1a into the paring chamber. Withinthe paring chamber 2 are radial vanes 3 securedtothe rotor body land vextending inward towardthe rotor EXlSzfl'OlTl the outer periphery of chamber 2. The vanes-3 serveto cause, rotation of the liquid entering the paringchamber from' below through passage 1a, as indicated by thearrows. A horizontal partition4 is secured to the vanes 3'directly above the inlet passage 1a and serves to: direct thelincoming liquid outwardly toward the periphery of the paring chamber. By. means of a locking ring 5,v the coverfl6jofthe .rotor is securedto the rest of the, rotor body.

'The cover 6 oftherotor 1 is provided with a central aperture 7, and. through this aperture extends a'stationary paring device-comprising a paring disc 8 anda discharge pipe .9. .The disc. 8 may be of conventional form and, as shown, has the usual paring channels 8a, the outer endsof which: extend into ..the rotating annular body of liquidin chamber 2 and scoop or-pareliquid-from this rotating body. The pared: liquid is forced inward through the paring channels 8a .and then upward through the -.discharge. pipe 9 .leading from these channels, the pipe 9 being.,concentric- .to. the rotonaxis. .Onthe outside ,of the .stationarydischarge pipe 9 isv a. metal wearing tube ltLhavinga polished outer surface which is surrounded and engaged by the inner sealing surface or leg of. a packing;. collar 11 of inverted U-shaped. cross-section. The outer leg of sealing collar 11. is securedin any suitable that collar 'll'rotates withthe rotor 1 whilethe inner'leg manner to the surrounding part of the rotor cover 6, so

- to lieat the radius 12. In the wall of the paring device 16in the collar packing 11.

89 are holes 13 which open into an annular space 14 between the outside of'the discharge pipe 9 and themside of a cylindrical projection 15, thalatter extending upward from the paring disc 8 into the annular recess Thus, some of the pared liquid flowing inward through paring channels 8a will pass throughthe holes 13 into space 14,where it contacts the inner leg of collar 11 and the lower portion'of wearing tube 10"to provide a cooling and lubricating "action.

From the annulars-pace 14,"the"liquid' flows 'over'the freeend'of cylindrical projection 15, then downward b'etween'the latter and the outer leg of collar" 11," and then outward intothe annular body of liqu'idiin paring chamberz;

Asgshown in'thei drawing, the annular recess" 16; of

packing collar 11 'faces'the interior of the rotor, softhat any'super-atrno'spheric pressure in paring -charnberf2'will serve to'press'the'collar against the wearing tube 10.

I claim: lfIna' centrifugal separator having a hollow rotor provided with a paring chamber from which a separated liquid'is tobe discharged through an hermetically closed".

cured to the rotor for rotation therewith andihavingfits inner leg surrounding and engaging the outside :fo'fthe stationary discharge pipe, said inner leg making' aslid ing'sealing' contact with said discharge pipe,the" packing collar forming an annular recess facing the inter-ror'of'the rotor, and *a cylindrical projection on theparingdevice' disposed"concentricallyto the rotor axis and'having a free' edge extending'into said annular recess, there being an' annularspace formedbetweenthe outside ofthedischarge pipe and the inside of'the cylindrical projection,

the paring device having a liquid supply channel opening into-said annular space.

2. The combinationaccording to claim 1,: in'which the liquid' supplychannel is an aperture 'in't-he wall'of the iparing-device; whereby liquid pared by said device enters said annular space byway of said aperture.

References Cited in the file 'of'thispatent UNITED STATES PATENTS Forsberg June ;9,:;1936 Andersson Jan. 2,: 1951 

